Merge #6852

6852: Ignore lifetime params in substitutions r=matklad a=Veykril

[`hir_ty::utils::Generics`](https://github.com/rust-analyzer/rust-analyzer/blob/master/crates/hir_ty/src/utils.rs#L153) currently only assumes type parameters but not lifetime parameters and therefor creates incorrect index and length calculations, this PR just makes the use sites ignore LifetimeGenerics for now.

This fixes the panic at least locally for me for `analysis-stats`. Funnily enough this panic prevented me from using reference search for the `args` field to fix this problem.

Co-authored-by: Lukas Wirth <lukastw97@gmail.com>

Author: bors[bot]

crates/hir_def/src/item_tree.rs

@@ -246,7 +246,10 @@ struct GenericParamsStorage {
 
 impl GenericParamsStorage {
     fn alloc(&mut self, params: GenericParams) -> GenericParamsId {
-        if params.types.is_empty() && params.where_predicates.is_empty() {
+        if params.types.is_empty()
+            && params.lifetimes.is_empty()
+            && params.where_predicates.is_empty()
+        {
             return GenericParamsId::EMPTY;
         }
 

crates/hir_ty/src/infer/expr.rs

@@ -856,7 +856,12 @@ impl<'a> InferenceContext<'a> {
         // handle provided type arguments
         if let Some(generic_args) = generic_args {
             // if args are provided, it should be all of them, but we can't rely on that
-            for arg in generic_args.args.iter().take(type_params) {
+            for arg in generic_args
+                .args
+                .iter()
+                .filter(|arg| matches!(arg, GenericArg::Type(_)))
+                .take(type_params)
+            {
                 match arg {
                     GenericArg::Type(type_ref) => {
                         let ty = self.make_ty(type_ref);

crates/hir_ty/src/lower.rs

@@ -565,7 +565,13 @@ fn substs_from_path_segment(
             if generic_args.has_self_type { self_params + type_params } else { type_params };
         let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
         // if args are provided, it should be all of them, but we can't rely on that
-        for arg in generic_args.args.iter().skip(skip).take(expected_num) {
+        for arg in generic_args
+            .args
+            .iter()
+            .filter(|arg| matches!(arg, GenericArg::Type(_)))
+            .skip(skip)
+            .take(expected_num)
+        {
             match arg {
                 GenericArg::Type(type_ref) => {
                     had_explicit_type_args = true;